Jittering during sliding operation

Hello everyone!

Certainly, the so-called... "Stalling" is a well-known and relatively common issue with older VP-TDIs.
Recently, my VP-TDI has also been stuttering. I want to describe the symptoms here in the forum because I also have another suspicion about the cause of the stuttering. Those TDI drivers who are experiencing these issues can certainly provide a quick assessment of the situation, especially since they are well-versed in the effects.

What really surprises me is the fact that the vibrations are most pronounced during the sliding operation, i.e. when the power input is 0. This is also the reason why I find it difficult to imagine a malfunctioning metering gear as the cause.
Additionally, there is a relatively sharply defined speed range between 1600 and 1800 1/min, in which the engine revs up noticeably when the engine is running at low load.

Do these symptoms indicate a classic "pumping jerkiness"?
Thank you for your support.

Greetings
Alex

Compression differences between individual cylinders can also cause jolting. Specifically in the described operating range. For example, a valve that no longer closes properly (a defective hydrostat, if applicable, not working properly) could be the cause. A short 'clunk' in one of the cylinders is also possible. (The experiences speak for themselves ) But then, a fault in the MSG should be assumed. Also, the lamp is blinking . Otherwise, it could also be the 'old' shaking . I wish you much success and low costs .

Hi Alex,

either the fuel injection amount does not completely return to zero (fuel pump top shifted?), a bit in the engine control unit is set to the wrong value, or a nozzle is leaking...
That would be the kind of things that would immediately come to mind.

Hello, Rainer

I am currently experiencing similar problems. Initially, I assumed that the issue was related to the quantity control system. I completely reinstalled it over the weekend, but unfortunately, it didn't help at all (although it's running a bit smoother).
My suspicion is that the problem lies with the hydraulic suspension components. During the installation of the engine heater, I noticed traces of a brown liquid on the underside. It is possible that the oil has hardened and that the bearings are now no longer providing damping. This weekend, I'll finally get around to finishing it.

Hello everyone!

So, the nozzles are only about 12,000 km old (complete nozzle holder combinations), which means I can rule out the possibility that one is leaking.
Also, the pump was not tampered with, meaning that the pump head is still factory-adjusted.
The MWB11 also only shows marginal differences between the cylinders when using VAG-COM, even when the readings are between 0 and 0.4 mg/H. When there are significant differences in compression, I claim that the amount of energy in the weak cylinder would be pulled upwards.
The engine itself performs well, offering excellent performance, consumes very little fuel, and almost no oil. These are actually indicators that point to a healthy engine.
The issue with the faulty hydro might be because the engine occasionally (even when warm) makes clacking noises.

One more thing that comes to mind regarding this topic: I've noticed on several occasions that the pump sometimes has trouble regulating the start of the spray. Perhaps the "start of spray" adjustment is causing the shaking, due to a stiff piston. If the pump never achieves the desired "start of spray" at its static operating points, but instead oscillates violently around the target value, both early and late, then... Is that still an explanation approach?

Greetings
Alex

donalexo wrote:

I've also noticed, while monitoring, that the pump sometimes has trouble regulating the start of the spray. Maybe the shaking is caused by the adjustment of the starting point, due to a stiff piston.

In a pure push with quantity zero (Your 1. (Posting) might not matter.

Quote:

If the pump never reaches the target injection start point when operating in static conditions, but instead oscillates violently around the target value, both early and late,

This could also be due to constant air supply in the diesel inlet:
Once a bubble passes through the outlet valve, the internal pressure of the pump collapses -> resulting in a late SB (Supervisory Break), followed by a corrective adjustment, after which the bubble disappears and the internal pressure of the pump rises again -> SB is set too early, etc.

However, if the diesel supply is air-free, then a stuck SV (fuel shut-off valve) is most likely the cause.

*digging out


A solution found? We had a similar problem just now (in another thread) where it turned out to be a clutch failure. We hadn't experienced this before, but there are always new experiences . You mentioned the possibility of a motor mount issue, did that turn out to be the case? Or, Ulf's theory about the air in the system?

Uhm, well, I haven't really made much progress with the stuttering problem yet.
Last weekend, I took a car with a faulty accelerator pedal to the track. It was incredibly responsive to the gas pedal, and sometimes it would "buck" or jerk when shifting gears. That's obvious, because the damping is missing.
However, at low speeds and under a load in the plane, I was no longer able to detect any jerking. As far as I can tell, my gear mechanism is therefore difficult to operate

Furthermore, I removed the LuFi box and had to realize that my gearbox bearing is hanging halfway on the 8th, meaning that during the clutch change, the workshop did not align the bearing parallel to the longitudinal beam, but simply fixed it somehow.
Likely, the "buzzing" noise in the sliding operation also originates from this aggregate connection. I've already bought the screws, but I'm short on time.

I will keep you updated on any changes once the inventory is re-aligned.

Greetings
Alex

Hi donalexo.

I had the exact same problem with one of my predecessor's 1z-Golfs. Slight vibration in the partial load range around 1400 - 1800 rpm (in 5th gear). Everything that VW had in stock was replaced. Initially, they just said 'but nobody drives so low' . After a short but intense discussion with the workshop manager and with a reference to the used car warranty that I would enforce through my legal protection, everything was replaced in a frenzy. The LMM, N87, NHG, EDC and finally the entire pump were replaced. I didn't pay a cent and then returned the car, as the vibration still occurred. Then the same problem occurred at the end of a 1993 Audi B4. Even with a NEW pump, it couldn't be solved. Since I didn't want to go through a swapping frenzy (with no guarantee), I also quickly resold the car. Only with the current PD (presumably referring to a specific document or policy) is there complete peace of mind.

Interestingly, the Golf ran perfectly with the replacement OT sender (NHG's OT replacement signal). However, the vibration damping was missing, and the tachometer doesn't display. But, as I said before, even the definitely NEW pump didn't solve the problem. First, the used car warranty .

Good luck

Hati wrote:

Only with the current PD (prescription) is there complete peace of mind.

The same goes for my ASZ (specific condition).
"Although he runs somewhat rough in the 1st second after a cold start, and the LL is also sometimes slightly unsteady, he has not shown any noticeable (and, in my opinion, much more annoying) vibrations from the widespread VP37 partial load in the low-speed range so far."

PD seems to represent a completely different software concept in the LL partial load transition area...

@ Hati:

I believe your comparison is somewhat flawed, because the 1Z still had a completely different generation of engine control unit (ECU) compared to the AGR/AHF.
Therefore, I am confident that cleaning the metering system and aligning the gearbox will improve the situation .

Overall, my throttle cable has become much stiffer due to the installation of the performance clutch (Sachs Performance), because the torsion springs are significantly stiffer. For those who are now curious: My AGR (Exhaust Gas Recirculation) system is from the very first series without ZMS (Zentralmotoraufhängung) and features a torsion-spring suspension on the clutch disc

Now, it would only be necessary to consider whether any installation errors (apart from the incorrectly aligned gearbox bearing) could be responsible for the jerking during installation. Does anyone have any ideas?

Greetings
Alex

Hi Alex.

I hope my comparison is accurate. Cleaning the MSW is significantly cheaper than a complete replacement, especially if you have to pay for the replacement yourself.
Furthermore, it's annoying to spend more time in the workshop than on the road.

I'm rooting for you!

The usual, well-known problems (especially after sloppy chip tuning)! The problem is that the inertia of the flywheel in this specific operating range is not sufficient to fully translate the torque caused by an excessive amount of fuel injected, regardless of whether it's an EMS or ZMS (failure is also possible here!). With a larger amount... However, this phenomenon of 'full load' disappears again, as the flywheel is sufficiently accelerated.

So, the only solution here is one. A software update for the lower load range!